One-step fabrication of titania hollow spheres by controlled interfacial reaction in a droplet-based microfluidic system

We present a facile ethanol-in-oil droplet-based microfluidic approach for one-step fabrication of titania hollow spheres through controlled interfacial reaction. The method combines microfluidic generation of uniform ethanol-in-oil droplets and subsequent in situ controlled interfacial reaction within the microfluidic channel. Ethanol-based droplets are suspended in an oil continuous phase containing titanium tertabutoxide. The small amount of water in the droplet phase diffuses to the interface leading to hydrolysis and condensation, and titania solidifies around the droplet forming titania microcapsules. The vigorous reaction between titanium tetrabutoxide and water is controlled by analyzing a mass transfer model, and then by selecting suitable continuous and dispersed phases. Highly viscous paraffin oil in combination with a low-viscosity ethanol-based droplet phase facilitates the successful formation of titania at the interface rather than in the continuous phase. This research provides a new approach for the controlled fabrication of titania microcapsules having uniform particle size and unique folded and crumpled structure.